This invention concerns the field of semiconductor material etching by wet process techniques.
In the fabrication of transistors and other semiconductor devices there is increasing need for precisely controllable processing steps, steps which can define small features in the semiconductor material layers of the device. In other words, there is need in the semiconductor art for processing such as in the defining of field-effect transistor gate region elements, i.e., processing capable of smaller physical sizes and more accurate feature position location than is presently feasible. Coincidentally with arising of this need, there has evolved apparatus and techniques capable of measuring the dimensions achieved by any such improved processing. The present invention relates to such improved processing in the area of wet process semiconductor material etching.
By way of contrast it is notable that the first digital etching techniques developed use gas and plasma chemical sources to perform the digital etch and may therefore be classified as dry processes. This invention is believed notable in its use of wet chemicals to perform both steps of a digital etch, forming a completely wet chemical digital etching technique.